Cellulose fiber insulation, hereinafter referred to as CFI, is increasingly used as insulating material for buildings. Its cost is much less than the mineral insulating materials, such as slag wool, glass fibers, and the like. Also, the great demand for insulation resulting from increased energy costs has created a serious shortage of mineral insulating materials. CFI is usually produced from waste paper or other waste cellulosic materials which are comminuted or otherwise reduced to small sizes. Since they are produced by purely mechanical means from material such as waste paper and other waste cellulosic materials that have little or no value, their cost is considerably less than slag wool, fiberglass, and the like. CFI is an excellent insulator but it is also flammable and so cannot be used without application of fire retardant materials, which are mandatory in practically all building codes; as a matter of fact, when properly treated with fire retardant CFI is a markedly better insulator than mineral insulators, such as glass wool, slag wool, and the like.
Numerous fire retardants have been used, the best at the present time being a mixture of boric acid and borax. Application to the CFI after comminution or during comminution has been effected either by applying dry chemicals or spraying on dispersions, such as solutions in water, during the manufacture of the CFI or after it has been manufactured. CFI treated with a boric acid-borax mixture has adequate fire resistance to meet building codes although, of course, not quite as fire resistant as the inorganic materials, such as glass fibers, slag wool, and the like. However, because of the lower cost of fire resistant CFI and the shortage of the mineral insulation, such as glass fibers, sometimes referred to as glass wool, there is an increasing demand for the cheaper CFI when rendered sufficiently fire resistant to meet building codes.
In the past CFI has been rendered fire resistant by applying mixtures of boric acid and borax, either in dry form, usually during the comminution of the CFI, or by spraying a liquid dispersion, such as a solution in water, which can be applied either during comminution of the CFI or even after it has been comminuted. The principal cost of the treatment is the relatively high cost of boric acid, which is produced from borax by treatment with acid and separating and/or purifying the boric acid produced. It is with a cheaper product containing boric acid and borax, without any loss of fire retardancy, and in fact a slight improvement, that the present invention deals.